Label and LabelLink models for implementing own GitLab labels

app/models/label.rb

+class Label < ActiveRecord::Base
+  belongs_to :project
+  has_many :label_links, dependent: :destroy
+
+  validates :color, format: { with: /\A\#[0-9A-Fa-f]{3}{1,2}+\Z/ }, allow_blank: true
+  validates :project, presence: true
+end

app/models/label_link.rb

+class LabelLink < ActiveRecord::Base
+  belongs_to :target, polymorphic: true
+  belongs_to :label
+
+  validates :target, presence: true
+  validates :label, presence: true
+end

db/migrate/20140729134820_create_labels.rb

+class CreateLabels < ActiveRecord::Migration
+  def change
+    create_table :labels do |t|
+      t.string :title
+      t.string :color
+      t.integer :project_id
+
+      t.timestamps
+    end
+  end
+end

db/migrate/20140729140420_create_label_links.rb

+class CreateLabelLinks < ActiveRecord::Migration
+  def change
+    create_table :label_links do |t|
+      t.integer :label_id
+      t.integer :target_id
+      t.string :target_type
+
+      t.timestamps
+    end
+  end
+end

db/schema.rb

@@ -11,7 +11,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 20140625115202) do
+ActiveRecord::Schema.define(version: 20140729140420) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
@@ -109,6 +109,22 @@ ActiveRecord::Schema.define(version: 20140625115202) do
 
   add_index "keys", ["user_id"], name: "index_keys_on_user_id", using: :btree
 
+  create_table "label_links", force: true do |t|
+    t.integer  "label_id"
+    t.integer  "target_id"
+    t.string   "target_type"
+    t.datetime "created_at"
+    t.datetime "updated_at"
+  end
+
+  create_table "labels", force: true do |t|
+    t.string   "title"
+    t.string   "color"
+    t.integer  "project_id"
+    t.datetime "created_at"
+    t.datetime "updated_at"
+  end
+
   create_table "merge_request_diffs", force: true do |t|
     t.string   "state"
     t.text     "st_commits"

spec/factories/label_links.rb

+# Read about factories at https://github.com/thoughtbot/factory_girl
+
+FactoryGirl.define do
+  factory :label_link do
+    label
+    target factory: :issue
+  end
+end

spec/factories/labels.rb

+# Read about factories at https://github.com/thoughtbot/factory_girl
+
+FactoryGirl.define do
+  factory :label do
+    title "Bug"
+    color "#990000"
+    project
+  end
+end

spec/models/label_link_spec.rb

+require 'spec_helper'
+
+describe LabelLink do
+  let(:label) { create(:label_link) }
+  it { label.should be_valid }
+
+  it { should belong_to(:label) }
+  it { should belong_to(:target) }
+end

spec/models/label_spec.rb

+require 'spec_helper'
+
+describe Label do
+  let(:label) { create(:label) }
+  it { label.should be_valid }
+
+  it { should belong_to(:project) }
+end